Liquid crystal display device having a cross-shaped pixel electrode

ABSTRACT

According to one embodiment, a liquid crystal display device includes a first substrate including a cross-shaped pixel electrode which includes a main pixel electrode and a sub-pixel electrode, and a second substrate including a common electrode which includes main common electrodes and sub-common electrodes. A first horizontal inter-electrode distance between the main pixel electrode and the main common electrode is less than a second horizontal inter-electrode distance between the sub-pixel electrode and the sub-common electrode and is greater than a vertical inter-electrode distance between the main pixel electrode and the main common electrode.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority fromprior Japanese Patent Application No. 2011-152103, filed Jul. 8, 2011,the entire contents of which are incorporated herein by reference.

FIELD

Embodiments described herein relate generally to a liquid crystaldisplay device.

BACKGROUND

In recent years, flat-panel display devices have been vigorouslydeveloped. By virtue of such advantageous features as light weight,small thickness and low power consumption, special attention has beenpaid to liquid crystal display devices among others. In particular, inactive matrix liquid crystal devices in which switching elements areincorporated in respective pixels, attention is paid to theconfiguration which makes use of a lateral electric field (including afringe electric field), such as an IPS (In-Plane Switching) mode or anFFS (Fringe Field Switching) mode. Such a liquid crystal display deviceof the lateral electric field mode includes pixel electrodes and acounter-electrode, which are formed on an array substrate, and liquidcrystal molecules are switched by a lateral electric field which issubstantially parallel to a major surface of the array substrate.

On the other hand, there has been proposed a technique wherein a lateralelectric field or an oblique electric field is produced between a pixelelectrode formed on an array substrate and a counter-electrode formed ona counter-substrate, thereby switching liquid crystal molecules.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view which schematically illustrates a structure and anequivalent circuit of a liquid crystal display panel according to anembodiment.

FIG. 2 is a plan view which schematically shows a structure example of apixel at a time when a liquid crystal display panel shown in FIG. 1 isviewed from a counter-substrate side.

FIG. 3 is a schematic cross-sectional view, taken along line A-A in FIG.2, showing a cross-sectional structure of the liquid crystal displaypanel shown in FIG. 2.

FIG. 4 is a view for explaining an electric field which is producedbetween a pixel electrode and a common electrode in the liquid crystaldisplay panel shown in FIG. 2, and a relationship between directors ofliquid crystal molecules by this electric field and a transmittance.

FIG. 5 is a schematic cross-sectional view of the liquid crystal displaypanel, for explaining alignment states of liquid crystal moleculesincluded in the liquid crystal layer in the embodiment.

FIG. 6 is a schematic cross-sectional view of a liquid crystal displaypanel, for explaining alignment states of liquid crystal moleculesincluded in a liquid crystal layer in a comparative example.

FIG. 7 is a plan view which schematically shows another structureexample of the pixel at a time when the liquid crystal display panelshown in FIG. 1 is viewed from the counter-substrate side.

FIG. 8 is a schematic cross-sectional view, taken along line B-B in FIG.7, showing a cross-sectional structure of a liquid crystal display panelwhich is combined with the array substrate shown in FIG. 7.

FIG. 9 is a plan view which schematically shows another structureexample of the pixel at a time when the liquid crystal display panelshown in FIG. 1 is viewed from the counter-substrate side.

DETAILED DESCRIPTION

In general, according to one embodiment, a liquid crystal display deviceincludes a first substrate including a cross-shaped pixel electrodewhich is disposed in a pixel having a less length in a first directionthan in a second direction crossing the first direction and includes amain pixel electrode extending in the second direction and a sub-pixelelectrode extending in the first direction, the first substrate furtherincluding a first alignment film which covers the pixel electrode and issubjected to alignment treatment in a first alignment treatmentdirection; a second substrate including a common electrode whichincludes main common electrodes extending in the second direction onboth sides of the main pixel electrode and sub-common electrodesextending in the first direction on both sides of the sub-pixelelectrode, the second substrate further including a second alignmentfilm which covers the common electrode and is subjected to alignmenttreatment in a second alignment treatment direction which is parallel tothe first alignment treatment direction; and a liquid crystal layerincluding liquid crystal molecules held between the first substrate andthe second substrate, wherein a first horizontal inter-electrodedistance in the first direction between the main pixel electrode and themain common electrode is less than a second horizontal inter-electrodedistance in the second direction between the sub-pixel electrode and thesub-common electrode and is greater than a vertical inter-electrodedistance between the main pixel electrode and the main common electrodein a third direction which is perpendicular to the first direction andthe second direction.

According to another embodiment, a liquid crystal display deviceincludes a first substrate including a first gate line and a second gateline which extend in a first direction, a first source line and a secondsource line which extend in a second direction crossing the firstdirection, a pixel electrode which includes a main pixel electrodeextending in the second direction between the first source line and thesecond source line and a sub-pixel electrode extending the firstdirection between the first gate line and the second gate line, firstshield electrodes which extend in the first direction and are opposed tothe first gate line and the second gate line, and a first alignment filmwhich covers the pixel electrode and the first shield electrodes and issubjected to alignment treatment in a first alignment treatmentdirection; a second substrate including a common electrode includingmain common electrodes which are opposed to the first source line andthe second source line and extend in the second direction, andsub-common electrodes which are opposed to the first shield electrodesand extend in the first direction, the second substrate furtherincluding a second alignment film which covers the common electrode andis subjected to alignment treatment in a second alignment treatmentdirection which is parallel to the first alignment treatment direction;and a liquid crystal layer including liquid crystal molecules heldbetween the first substrate and the second substrate, wherein a firsthorizontal inter-electrode distance in the first direction between themain pixel electrode and the main common electrode is less than a secondhorizontal inter-electrode distance in the second direction between thesub-pixel electrode and each of the first shield electrode and thesub-common electrode, and is greater than a vertical inter-electrodedistance between the main pixel electrode and the main common electrodein a third direction which is perpendicular to the first direction andthe second direction.

According to another embodiment, a liquid crystal display deviceincludes a first substrate including a cross-shaped pixel electrodewhich includes a sub-pixel electrode extending a first direction and amain pixel electrode extending in a second direction crossing the firstdirection, the main pixel electrode having a greater length than thesub-pixel electrode, the first substrate further including a firstalignment film which covers the pixel electrode and is subjected toalignment treatment in a first alignment treatment direction; a secondsubstrate including a common electrode which includes main commonelectrodes extending in the second direction on both sides of the mainpixel electrode and sub-common electrodes extending in the firstdirection on both sides of the sub-pixel electrode, the second substratefurther including a second alignment film which covers the commonelectrode and is subjected to alignment treatment in a second alignmenttreatment direction which is parallel and identical to the firstalignment treatment direction; and a liquid crystal layer includingliquid crystal molecules held between the first substrate and the secondsubstrate, wherein an initial alignment direction of the liquid crystalmolecules in a state, in which an electric field is not produced betweenthe pixel electrode and the common electrode, is substantially parallelto a direction of extension of the main pixel electrode, and a firsthorizontal inter-electrode distance in the first direction between themain pixel electrode and the main common electrode is less than a secondhorizontal inter-electrode distance in the second direction between thesub-pixel electrode and the sub-common electrode and is greater than avertical inter-electrode distance between the main pixel electrode andthe main common electrode in a third direction which is perpendicular tothe first direction and the second direction.

Embodiments will now be described in detail with reference to theaccompanying drawings. In the drawings, structural elements having thesame or similar functions are denoted by like reference numerals, and anoverlapping description is omitted.

FIG. 1 is a view which schematically shows a structure and an equivalentcircuit of a liquid crystal display device according to an embodiment.

Specifically, the liquid crystal display device includes anactive-matrix-type liquid crystal display panel LPN. The liquid crystaldisplay panel LPN includes an array substrate AR which is a firstsubstrate, a counter-substrate CT which is a second substrate that isdisposed to be opposed to the array substrate AR, and a liquid crystallayer LQ which is disposed between the array substrate AR and thecounter-substrate CT. The liquid crystal display panel LPN includes anactive area ACT which displays an image. The active area ACT is composedof a plurality of pixels PX which are arrayed in a matrix of m×n (m andn are positive integers).

The liquid crystal display panel LPN includes, in the active area ACT,an n-number of gate lines G (G1 to Gn), an n-number of storagecapacitance lines C (C1 to Cn), and an m-number of source lines S (S1 toSm). The gate lines G and storage capacitance lines C extendsubstantially linearly, for example, in a first direction X. The gatelines G and storage capacitance lines C neighbor at intervals along asecond direction Y crossing the first direction X, and are alternatelyarranged in parallel. In this example, the first direction X and thesecond direction Y are perpendicular to each other. The source lines Scross the gate lines G and storage capacitance lines C. The lines Sextend substantially linearly along the second direction Y. It is notalways necessary that each of the gate lines G, storage capacitancelines C and source lines S extend linearly, and a part thereof may bebent.

Each of the gate lines G is led out of the active area ACT and isconnected to a gate driver GD. Each of the source lines S is led out ofthe active area ACT and is connected to a source driver SD. At leastparts of the gate driver GD and source driver SD are formed on, forexample, the array substrate AR, and are connected to a driving IC chip2 which incorporates a controller.

Each of the pixels PX includes a switching element SW, a pixel electrodePE and a common electrode CE. A storage capacitance CS is formed, forexample, between the storage capacitance line C and the pixel electrodePE. The storage capacitance line C is electrically connected to avoltage application module VCS to which a storage capacitance voltage isapplied.

In the present embodiment, the liquid crystal display panel LPN isconfigured such that the pixel electrodes PE are formed on the arraysubstrate AR, and at least a part of the common electrode CE is formedon the counter-substrate CT, and liquid crystal molecules of the liquidcrystal layer LQ are switched by mainly using an electric field which isproduced between the pixel electrodes PE and the common electrode CE.The electric field, which is produced between the pixel electrodes PEand the common electrode CE, is an oblique electric field which isslightly inclined to an X-Y plane which is defined by the firstdirection X and second direction Y, or to a substrate major surface ofthe array substrate AR or a substrate major surface of thecounter-substrate CT (or a lateral electric field which is substantiallyparallel to the substrate major surface).

The switching element SW is composed of, for example, an n-channelthin-film transistor (TFT). The switching element SW is electricallyconnected to the gate line G and source line S. The switching element SWmay be of a top gate type or a bottom gate type. In addition, asemiconductor layer of the switching element SW is formed of, forexample, polysilicon, but it may be formed of amorphous silicon.

The pixel electrodes PE are disposed in the respective pixels PX, andare electrically connected to the switching elements SW. The commonelectrode CE has, for example, a common potential, and is disposedcommon to the pixel electrodes PE of plural pixels PX via the liquidcrystal layer LQ. The pixel electrodes PE and common electrode CE areformed of a light-transmissive, electrically conductive material such asindium tin oxide (ITO) or indium zinc oxide (IZO). However, the pixelelectrodes PE and common electrode CE may be formed of other metallicmaterial such as aluminum.

The array substrate AR includes a power supply module VS for applying avoltage to the common electrode CE. The power supply module VS isformed, for example, on the outside of the active area ACT. The commonelectrode CE is led out to the outside of the active area ACT, and iselectrically connected to the power supply module VS via an electricallyconductive member (not shown).

FIG. 2 is a plan view which schematically shows a structure example ofone pixel PX at a time when the liquid crystal display panel LPN shownin FIG. 1 is viewed from the counter-substrate side. FIG. 2 is a planview in an X-Y plane.

A gate line G1, a gate line G2 and a storage capacitance line C1 extendin the first direction X. A source line S1 and a source line S2 extendin the second direction Y. The storage capacitance line C1 is located ata substantially middle point between the gate line G1 and the gate lineG2. Specifically, the distance between the gate line G1 and the storagecapacitance line C1 in the second direction Y is substantially equal tothe distance between the gate line G2 and the storage capacitance lineC1 in the second direction Y.

In the example illustrated, the pixel PX corresponds to a grid regionwhich is formed by the gate line G1, gate line G2, source line S1 andsource line S2, as indicated by a broken line in FIG. 2. The pixel PXhas a rectangular shape having a greater length in the second directionY than in the first direction X. The length of the pixel PX in the firstdirection X corresponds to a pitch between the source line S1 and sourceline S2 in the first direction X. The length of the pixel PX in thesecond direction Y corresponds to a pitch between the gate line G1 andgate line G2 in the second direction Y. The length of the pixel PX inthe second direction Y is about three times greater than the length ofthe pixel PX in the first direction X. The pixel electrode PE isdisposed between the source line S1 and source line S2 which neighboreach other. In addition, the pixel electrode PE is located between thegate line C1 and gate line G2.

In the example illustrated, in the pixel PX, the source line S1 isdisposed at a left side end portion, the source line S2 is disposed at aright side end portion, the gate line G1 is disposed at an upper sideend portion, and the gate line G2 is disposed at a lower side endportion. Strictly speaking, the source line S1 is disposed to extendover a boundary between the pixel PX and a pixel neighboring on the leftside, the source line S2 is disposed to extend over a boundary betweenthe pixel PX and a pixel neighboring on the right side, the gate line G1is disposed to extend over a boundary between the pixel PX and a pixelneighboring on the upper side, and the gate line G2 is disposed toextend over a boundary between the pixel PX and a pixel neighboring onthe lower side. The storage capacitance line C1 is disposed at asubstantially central part of the pixel PX.

A switching element SW in the illustrated example is electricallyconnected to the gate line G1 and source line S1. The switching elementSW is provided at an intersection between the gate line G1 and sourceline S1. A drain line of the switching element SW is formed to extendalong the source line S1 and storage capacitance line C1, and iselectrically connected to the pixel electrode PE via a contact hole CHformed in an area overlapping the storage capacitance line C1. Theswitching element SW is provided in an area overlapping the source lineS1 and storage capacitance line C1, and does not substantially protrudefrom the area overlapping the source line S1 and storage capacitanceline C1, thus suppressing a decrease in area of an aperture portionwhich contributes to display.

The pixel electrode PE includes a main pixel electrode PA and asub-pixel electrode PB. The main pixel electrode PA and sub-pixelelectrode PB are formed to be integral or continuous, and areelectrically connected to each other. In the meantime, in the exampleillustrated, only the pixel electrode PE which is disposed in one pixelPX is shown, but pixel electrodes of the same shape are disposed inother pixels, the depiction of which is omitted.

The main pixel electrode PA is located between the source line S1 andsource line S2. In the illustrated example, the sub-pixel electrode PBcrosses an intermediate portion in the second direction Y of the mainpixel electrode PA. Accordingly, the main pixel electrode PA linearlyextends in the second direction Y from the intersection with thesub-pixel electrode PB to the vicinity of the upper side end portion ofthe pixel PX and to the vicinity of the lower side end portion of thepixel PX. In other words, the main pixel electrode PA extends from theintersection with the sub-pixel electrode PB towards the gate line G1and gate line G2. Specifically, the pixel electrode PE is formed in across shape. In addition, the main pixel electrode PA is disposed at asubstantially middle position between the source line S1 and source lineS2, that is, at a center of the pixel PX. The distance in the firstdirection X between the source line S1 and the main pixel electrode PAis substantially equal to the distance in the first direction X betweenthe source line S2 and the main pixel electrode PA. The main pixelelectrode PA is formed in a strip shape having a substantially equalwidth in the first direction X.

The sub-pixel electrode PB crosses the main pixel electrode PA andextends along the first direction X. The sub-pixel electrode PB linearlyextends in the first direction X from the intersection with the mainpixel electrode PA to the vicinity of the left side end portion of thepixel PX and to the vicinity of the right side end portion of the pixelPX. In other words, the sub-pixel electrode PB linearly extends from theintersection with the main pixel electrode PA toward the source line S1and source line S2. In addition, the sub-pixel electrode PB is disposedat a substantially middle position between the gate line G1 and gateline G2, that is, at the center of the pixel PX. The distance in thesecond direction Y between the gate line G1 and the sub-pixel electrodePB is substantially equal to the distance in the second direction Ybetween the gate line G2 and the sub-pixel electrode PB. The sub-pixelelectrode PB is formed in a strip shape having a substantially equalwidth in the second direction Y. Furthermore, the sub-pixel electrode PBis opposed to the storage capacitance line C1. In other words, thestorage capacitance line C1 is located under the sub-pixel electrode PB.

Specifically, the entirety of the sub-pixel electrode PB is located inan area overlapping the storage capacitance line C1. The sub-pixelelectrode PB is electrically connected to the switching element SW viathe contact hole CH. The sub-pixel electrode PB is formed with a greaterwidth than the main pixel electrode PA. In addition, the length of themain pixel electrode PA in the second direction Y is greater than thelength of the sub-pixel electrode PB in the first direction X.

The common electrode CE includes main common electrodes CA andsub-common electrodes CB. The main common electrodes CA and sub-commonelectrodes CB are formed to be integral or continuous with each other,and are electrically to each other. Specifically, the common electrodeCE is formed in a grid shape in a manner to surround the pixel.

The main common electrodes CA extend, in the X-Y plane, linearly in thesecond direction Y that is substantially parallel to the main pixelelectrode PA, on both sides of the main pixel electrode PA.Alternatively, the main common electrodes CA are opposed to the sourcelines S which extend in the second direction Y, and extend substantiallyin parallel to the main pixel electrode PA. Specifically, the sourcelines S are located under the main common electrodes CA. The main commonelectrode CA is formed in a strip shape having a substantially equalwidth in the first direction X. In the example illustrated, two maincommon electrodes CA are arranged in parallel with a distance in thefirst direction X. Specifically, the main common electrodes CA include amain common electrode CAL disposed at the left side end portion of thepixel PX, and a main common electrode CAR disposed at the right side endportion of the pixel PX. Strictly speaking, the main common electrodeCAL is disposed to extend over a boundary between the pixel PX and apixel neighboring on the left side, and the main common electrode CAR isdisposed to extend over a boundary between the pixel PX and a pixelneighboring on the right side. The main common electrode CAL is opposedto the source line S1, and the main common electrode CAR is opposed tothe source line S2. The main common electrode CAL and the main commonelectrode CAR are electrically connected to each other within the activearea or outside the active area.

The sub-common electrodes CB extend, in the X-Y plane, linearly in thefirst direction X that is substantially parallel to the sub-pixelelectrode PB, on both sides of the sub-pixel electrode PB.Alternatively, the sub-common electrodes CB are opposed to the gatelines G which extend in the first direction X, and extend substantiallyin parallel to the sub-pixel electrode PB. Specifically, the gate linesG are located under the sub-common electrodes CB. The sub-commonelectrode CB is formed in a strip shape having a substantially equalwidth in the second direction Y. In the example illustrated, twosub-common electrodes CB are arranged in parallel with a distance in thesecond direction Y. Specifically, the sub-common electrodes CB include asub-common electrode CBU disposed at the upper side end portion of thepixel PX, and a sub-common electrode CBB disposed at the lower side endportion of the pixel PX. Strictly speaking, the sub-common electrode CBUis disposed to extend over a boundary between the pixel PX and a pixelneighboring on the upper side, and the sub-common electrode CBB isdisposed to extend over a boundary between the pixel PX and a pixelneighboring on the lower side. The sub-common electrode CBU is opposedto the gate line G1, and the sub-common electrode CBB is opposed to thegate line G2.

Paying attention to the positional relationship between the pixelelectrode PE and the common electrode CE, the common electrode CE doesnot overlap the pixel electrode PE in the X-Y plane. The main pixelelectrode PA and the main common electrodes CA are alternately arrangedalong the first direction X. One main pixel electrode PA is locatedbetween the main common electrode CAL and main common electrode CARwhich neighbor each other. In other words, the main common electrode CALand main common electrode CAR are disposed on both sides of a positionimmediately above the main pixel electrode PA. Alternatively, the mainpixel electrode PA is disposed between the main common electrode CAL andmain common electrode CAR. Thus, the main common electrode CAL, mainpixel electrode PA and main common electrode CAR are arranged in thenamed order along the first direction X. The main pixel electrode PA islocated at a substantially middle point between the main commonelectrode CAL and main common electrode CAR. Specifically, the distancebetween the main common electrode CAL and the main pixel electrode PA inthe first direction X is substantially equal to the distance between themain common electrode CAR and the main pixel electrode PA in the firstdirection X. In the present embodiment, the distance between the maincommon electrode CA and the main pixel electrode PA in the firstdirection X, that is, the distance between an edge of the main pixelelectrode PA and an edge of the main common electrode CA, which areopposed to each in the X-Y plane, is referred to as “first horizontalinter-electrode distance HD”.

In the X-Y plane, the sub-pixel electrode PB and the sub-commonelectrodes CB are alternately arranged along the second direction Y. Onesub-pixel electrode PB is located between the sub-common electrode CBUand sub-common electrode CBB which neighbor each other. In other words,the sub-common electrode CBU and sub-common electrode CBB are disposedon both sides of a position immediately above the sub-pixel electrodePB. Alternatively, the sub-pixel electrode PB is disposed between thesub-common electrode CBU and sub-common electrode CBB. Thus, thesub-common electrode CBB, sub-pixel electrode PB and sub-commonelectrode CBU are arranged in the named order along the second directionY. The sub-pixel electrode PB is located at a substantially middle pointbetween the sub-common electrode CBU and sub-common electrode CBB.Specifically, the distance between the sub-common electrode CBU and thesub-pixel electrode PB in the second direction Y is substantially equalto the distance between the sub-common electrode CBB and the sub-pixelelectrode PB in the second direction Y. In the present embodiment, thedistance between the sub-common electrode CB and the sub-pixel electrodePB in the second direction Y, that is, the distance between an edge ofthe sub-pixel electrode PB and an edge of the sub-common electrode CB,which are opposed to each in the X-Y plane, is referred to as “secondhorizontal inter-electrode distance YD”.

The first horizontal inter-electrode distance HD is less than the secondhorizontal inter-electrode distance YD. The second horizontalinter-electrode distance YD is double or more greater than the firsthorizontal inter-electrode distance HD. Since the length of the pixel PXin the second direction Y is about three times the length of the pixelPX in the first direction X, the second horizontal inter-electrodedistance YD is about three times the first horizontal inter-electrodedistance HD.

FIG. 3 is a schematic cross-sectional view, taken along line A-A in FIG.2, showing a cross-sectional structure of the liquid crystal displaypanel LPN shown in FIG. 2. FIG. 3 shows only parts which are necessaryfor the description.

A backlight 4 is disposed on the back side of the array substrate ARwhich constitutes the liquid crystal display panel LPN. Various modesare applicable to the backlight 4. As the backlight 4, use may be madeof either a backlight which utilizes a light-emitting diode (LED) as alight source, or a backlight which utilizes a cold cathode fluorescentlamp (CCFL) as a light source. A description of the detailed structureof the backlight 4 is omitted.

The array substrate AR is formed by using a first insulative substrate10 having light transmissivity. Source lines S are formed on a firstinterlayer insulation film 11, and are covered with a second interlayerinsulation film 12. Gate lines and storage capacitance lines, which arenot shown, are disposed, for example, between the first insulativesubstrate 10 and the first interlayer insulation film 11. Pixelelectrodes PE are formed on the second interlayer insulation film 12.Each pixel electrode PE is located on the inside of a positionimmediately above each of neighboring source lines S. A first alignmentfilm AL1 is disposed on that surface of the array substrate AR, which isopposed to the counter-substrate CT, and the first alignment film AL1extends over substantially the entirety of the active area ACT. Thefirst alignment film AL1 covers the pixel electrode PE, etc., and isalso disposed over the second interlayer insulation film 12. The firstalignment film AL1 is formed of a material which exhibits horizontalalignment properties. In the meantime, the array substrate AR mayinclude a part of the common electrode CE.

The counter-substrate CT is formed by using a second insulativesubstrate 20 having light transmissivity. The counter-substrate CTincludes a black matrix BM, a color filter CF, an overcoat layer OC, acommon electrode CE, and a second alignment film AL2.

The black matrix BM partitions the pixels PX and forms aperture portionsAP which are opposed to the pixel electrodes PE. Specifically, the blackmatrix BM is disposed so as to be opposed to wiring portions, such asthe source lines S, gate lines, storage capacitance lines, and switchingelements. In this example, only those portions of the black matrix BM,which extend in the second direction Y, are depicted, but the blackmatrix BM may include portions extending in the first direction X. Theblack matrix BM is disposed on an inner surface 20A of the secondinsulative substrate 20, which is opposed to the array substrate AR.

The color filter CF is disposed in association with each pixel PX.Specifically, the color filter CF is disposed in the aperture portion APon the inner surface 20A of the second insulative substrate 20, and apart of the color filter CF extends over the black matrix BM. Colorfilters CF, which are disposed in the pixels PX neighboring in the firstdirection X, have mutually different colors. For example, the colorfilters CF are formed of resin materials which are colored in threeprimary colors of red, blue and green. A red color filter CFR, which isformed of a resin material that is colored in red, is disposed inassociation with a red pixel. A blue color filter CFB, which is formedof a resin material that is colored in blue, is disposed in associationwith a blue pixel. A green color filter CFG, which is formed of a resinmaterial that is colored in green, is disposed in association with agreen pixel. Boundaries between these color filters CF are located atpositions overlapping the black matrix BM. The overcoat layer OC coversthe color filters CF. The overcoat layer OC reduces the effect ofasperities on the surface of the color filters CF. The overcoat layer OCis formed of, for example, a transparent resin material.

The common electrode CE is formed on that side of the overcoat layer OC,which is opposed to the array substrate AR. The main common electrodesCA are located above the source line S. The second alignment film AL2 isdisposed on that surface of the counter-substrate CT, which is opposedto the array substrate AR, and the second alignment film AL2 extendsover substantially the entirety of the active area ACT. The secondalignment film AL2 covers the common electrodes CE and overcoat layerOC. The second alignment film AL2 is formed of a material which exhibitshorizontal alignment properties.

The distance between the common electrodes CE and the pixel electrodesPE in a third direction Z is substantially constant. The third directionZ corresponds to a direction which is perpendicular to the firstdirection X and second direction Y, or corresponds to a normal directionof the liquid crystal display panel LPN. In the present embodiment, adistance between the common electrode CE and the pixel electrode PE inthe third direction Z, that is, a distance in the third direction Zbetween a surface of the pixel electrode PE and a surface of the commonelectrode CE, which are opposed to each other in the X-Z plane, isreferred to as “vertical inter-electrode distance VD”. The firsthorizontal inter-electrode distance HD between the pixel electrode PEand the common electrode CE is greater than the vertical inter-electrodedistance VD between the pixel electrode PE and the common electrode CE.

The first alignment film AL1 and second alignment film AL2 are subjectedto alignment treatment (e.g. rubbing treatment or optical alignmenttreatment) for initially aligning the liquid crystal molecules of theliquid crystal layer LQ. A first alignment treatment direction PD1, inwhich the first alignment film AL1 initially aligns the liquid crystalmolecules, is parallel to a second alignment treatment direction PD2, inwhich the second alignment film AL2 initially aligns the liquid crystalmolecules. In an example shown in part (A) of FIG. 2, the firstalignment treatment direction PD1 and second alignment treatmentdirection PD2 are parallel to each other and are identical. In anexample shown in part (B) of FIG. 2, the first alignment treatmentdirection PD1 and second alignment treatment direction PD2 are parallelto each other and are opposite to each other.

The above-described array substrate AR and counter-substrate CT aredisposed such that their first alignment film AL1 and second alignmentfilm AL2 are opposed to each other. In this case, columnar spacers,which are formed of, e.g. a resin material so as to be integral to oneof the array substrate AR and counter-substrate CT, are disposed betweenthe first alignment film AL1 of the array substrate AR and the secondalignment film AL2 of the counter-substrate CT. Thereby, a predeterminedcell gap, for example, a cell gap of 2 to 7 μm, is created. The arraysubstrate AR and counter-substrate CT are attached by a sealant SB onthe outside of the active area ACT in the state in which thepredetermined cell gap is created therebetween. The cell gap, in thiscontext, is substantially equivalent to the above-described verticalinter-electrode distance VD.

The liquid crystal layer LQ is held in the cell gap which is createdbetween the array substrate AR and the counter-substrate CT, and isdisposed between the first alignment film AL1 and second alignment filmAL2. The liquid crystal layer LQ includes liquid crystal molecules LM.The liquid crystal layer LQ is composed of a liquid crystal materialhaving a positive (positive-type) dielectric constant anisotropy.

A first optical element OD1 is attached, by, e.g. an adhesive, to anouter surface of the array substrate AR, that is, an outer surface 10Bof the first insulative substrate 10 which constitutes the arraysubstrate AR. The first optical element OD1 is located on that side ofthe liquid crystal display panel LPN, which is opposed to the backlight4, and controls the polarization state of incident light which entersthe liquid crystal display panel LPN from the backlight 4. The firstoptical element OD1 includes a first polarizer PL1 having a firstpolarization axis (or first absorption axis) AX1. In the meantime,another optical element, such as a retardation plate, may be disposedbetween the first polarizer PL1 and the first insulative substrate 10.

A second optical element OD2 is attached, by, e.g. an adhesive, to anouter surface of the counter-substrate CT, that is, an outer surface 20Bof the second insulative substrate 20 which constitutes thecounter-substrate CT. The second optical element OD2 is located on thedisplay surface side of the liquid crystal display panel LPN, andcontrols the polarization state of emission light emerging from theliquid crystal display panel LPN. The second optical element OD2includes a second polarizer PL2 having a second polarization axis (orsecond absorption axis) AX2. In the meantime, another optical element,such as a retardation plate, may be disposed between the secondpolarizer PL2 and the second insulative substrate 20.

The first polarization axis AX1 of the first polarizer PL1 and thesecond polarization axis AX2 of the second polarizer PL2 have apositional relationship of crossed Nicols. In this case, one of thepolarizers is disposed such that the polarization axis thereof isparallel or perpendicular to an initial alignment direction of liquidcrystal molecules LM, that is, the first alignment treatment directionPD1 or second alignment treatment direction PD2. When the initialalignment direction is parallel to the second direction Y, thepolarization axis of one polarizer is parallel to the second direction Yor is parallel to the first direction X.

In an example shown in part (a) of FIG. 2, the first polarizer PL1 isdisposed such that the first polarization axis AX1 thereof isperpendicular to the second direction Y that is the initial alignmentdirection of liquid crystal molecules LM, and the second polarizer PL2is disposed such that the second polarization axis AX2 thereof isparallel to the initial alignment direction of liquid crystal moleculesLM. In addition, in an example shown in part (b) of FIG. 2, the secondpolarizer PL2 is disposed such that the second polarization axis AX2thereof is perpendicular to the second direction Y that is the initialalignment direction of liquid crystal molecules LM, and the firstpolarizer PL1 is disposed such that the first polarization axis AX1thereof is parallel to the initial alignment direction of liquid crystalmolecules LM.

Next, the operation of the liquid crystal display panel LPN having theabove-described structure is described with reference to FIG. 2 and FIG.3.

Specifically, in a state in which no voltage is applied to the liquidcrystal layer LQ, that is, in a state (OFF time) in which no electricfield is produced between the pixel electrode PE and common electrodeCE, the liquid crystal molecule LM of the liquid crystal layer LQ isaligned such that the major axis thereof is positioned in the firstalignment treatment direction PD1 of the first alignment film AL1 andthe second alignment treatment direction PD2 of the second alignmentfilm AL2. This OFF time corresponds to the initial alignment state, andthe alignment direction of the liquid crystal molecule LM at the OFFtime corresponds to the initial alignment direction.

Strictly speaking, the liquid crystal molecule LM is not always alignedin parallel to the X-Y plane, and, in many cases, the liquid crystalmolecule LM is pre-tilted. Thus, the initial alignment direction of theliquid crystal molecule LM corresponds to a direction in which the majoraxis of the liquid crystal molecule LM at the OFF time is orthogonallyprojected onto the X-Y plane. In the description below, for the purposeof simplicity, it is assumed that the liquid crystal molecule LM isaligned in parallel to the X-Y plane, and the liquid crystal molecule LMrotates in a plane parallel to the X-Y plane.

In this case, each of the first alignment treatment direction PD1 andthe second alignment treatment direction PD2 is substantially parallelto the second direction Y. At the OFF time, the liquid crystal moleculeLM is initially aligned such that the major axis thereof issubstantially parallel to the second direction Y, as indicated by abroken line in FIG. 2. Specifically, the initial alignment direction ofthe liquid crystal molecule LM is parallel to the second direction Y (or0° to the second direction Y).

When the first alignment treatment direction PD1 and the secondalignment treatment direction PD2 are parallel and identical to eachother, as in the example illustrated, the liquid crystal molecules LMare substantially horizontally aligned (the pre-tilt angle issubstantially zero) in the middle part of the liquid crystal layer LQ inthe cross section of the liquid crystal layer LQ, and the liquid crystalmolecules LM are aligned with such pre-tilt angles that the liquidcrystal molecules LM become symmetric in the vicinity of the firstalignment film AL1 and in the vicinity of the second alignment film AL2,with respect to the middle part as the boundary (splay alignment). Inthe state in which the liquid crystal molecules LM are splay-aligned,optical compensation can be made by the liquid crystal molecules LM inthe vicinity of the first alignment film AL1 and the liquid crystalmolecules LM in the vicinity of the second alignment film AL2, even in adirection inclined to the normal direction of the substrate. Therefore,when the first alignment treatment direction PD1 and the secondalignment treatment direction PD2 are parallel and identical to eachother, light leakage is small in the case of black display, a highcontrast ratio can be realized, and the display quality can be improved.

In the meantime, when the first alignment treatment direction PD1 andthe second alignment treatment direction PD2 are parallel and oppositeto each other, the liquid crystal molecules LM are aligned withsubstantially equal pre-tilt angles, in the cross section of the liquidcrystal layer LQ, in the vicinity of the first alignment film AL1, inthe vicinity of the second alignment film AL2, and in the middle part ofthe liquid crystal layer LQ (homogeneous alignment).

Part of light from the backlight 4 passes through the first polarizerPL1 and enters the liquid crystal display panel LPN. The polarizationstate of the light, which enters the liquid crystal display panel LPN,is linear polarization perpendicular to the first polarization axis AX1of the first polarizer PL1. The polarization state of such linearpolarization hardly varies when the light passes through the liquidcrystal display panel LPN at the OFF time. Thus, the linearly polarizedlight, which has passed through the liquid crystal display panel LPN, isabsorbed by the second polarizer PL2 that is in the positionalrelationship of crossed Nicols in relation to the first polarizer PL1(black display).

On the other hand, in a state in which a voltage is applied to theliquid crystal layer LQ, that is, in a state (ON time) in which apotential difference is produced between the pixel electrode PE andcommon electrode CE, a lateral electric field (or an oblique electricfield), which is substantially parallel to the substrates, is producedbetween the pixel electrode PE and the common electrode CE. The liquidcrystal molecules LM are affected by the electric field, and the majoraxes thereof rotate within a plane which is parallel to the X-Y plane,as indicated by solid lines in the Figure.

In the example shown in FIG. 2, the liquid crystal molecule LM in alower half part of the region between the pixel electrode PE and maincommon electrode CAL rotates clockwise relative to the second directionY, and is aligned in a lower left direction in the Figure. The liquidcrystal molecule LM in an upper half part of the region between thepixel electrode PE and main common electrode CAL rotatescounterclockwise relative to the second direction Y, and is aligned inan upper left direction in the Figure. The liquid crystal molecule LM ina lower half part of the region between the pixel electrode PE and maincommon electrode CAR rotates counterclockwise relative to the seconddirection Y, and is aligned in a lower right direction in the Figure.The liquid crystal molecule LM in an upper half part of the regionbetween the pixel electrode PE and main common electrode CAR rotatesclockwise relative to the second direction Y, and is aligned in an upperright direction in the Figure.

As has been described above, in the state in which the electric field isproduced between the pixel electrode PE and common electrode CE in eachpixel PX, the liquid crystal molecules LM are aligned in a plurality ofdirections, with boundaries at positions overlapping the pixel electrodePE, and domains are formed in the respective alignment directions.Specifically, a plurality of domains are formed in one pixel PX.

At such ON time, linearly polarized light perpendicular to the firstpolarization axis AX1 of the first polarizer PL1 enters the liquidcrystal display panel LPN, and the polarization state of the lightvaries depending on the alignment state of the liquid crystal moleculesLM when the light passes through the liquid crystal layer LQ. At the ONtime, at least part of the light emerging from the liquid crystal layerLQ passes through the second polarizer PL2 (white display).

FIG. 4 is a view for explaining an electric field which is producedbetween the pixel electrode PE and common electrode CE in the liquidcrystal display panel LPN shown in FIG. 2, and a relationship betweendirectors of liquid crystal molecules LM by this electric field and atransmittance.

In the OFF state, the liquid crystal molecules LM are initially alignedin a direction which is substantially parallel to the second directionY. In the ON state in which a potential difference is produced betweenthe pixel electrode PE and the common electrode CE, when the director ofthe liquid crystal molecule LM (or the major-axis direction of theliquid crystal molecule LM) deviates by about 45° from the firstpolarization axis AX1 of the first polarizer PL1 and from the secondpolarization axis AX2 of the second polarizer PL2 in the X-Y plane, theoptical modulation ratio of the liquid crystal layer LQ is highest (i.e.the transmittance at the aperture portion is highest).

In the example illustrated, in the ON state, the director of the liquidcrystal molecule LM between the main common electrode CAL and the pixelelectrode PE is substantially parallel to a 45°-225° azimuth directionin the X-Y plane, and the director of the liquid crystal molecule LMbetween the main common electrode CAR and the pixel electrode PE issubstantially parallel to a 135°-315° azimuth direction in the X-Yplane, and a peak transmittance is obtained. Meanwhile, when thedirector of the liquid crystal molecule LM is substantially parallel toa 0°-180° azimuth direction in the X-Y plane or substantially parallelto a 90°-270° azimuth direction in the X-Y plane, the transmittance atthe aperture portion becomes lowest.

In the ON state, if attention is paid to the transmittance distributionper pixel, the liquid crystal molecules LM over the pixel electrode PEand common electrode CE hardly rotate from the initial alignmentdirection. In other words, the directors of the liquid crystal moleculesLM over the pixel electrode PE and common electrode CE are substantiallyparallel to the 90°-270° azimuth direction. Thus, the transmittance overthe pixel electrode PE and common electrode CE is substantially zero. Onthe other hand, a high transmittance can be obtained over almost theentire area of the inter-electrode gaps between the pixel electrode PEand the common electrode CE.

Each of the main common electrode CAL that is located immediately abovethe source line S1 and the main common electrode CAR that is locatedimmediately above the source line S2 is opposed to the black matrix BM.Each of the main common electrode CAL and main common electrode CAR hasa width which is equal to or less than the width of the black matrix BMin the first direction X, and does not extend toward the pixel electrodePE from the position overlapping the black matrix BM. Thus, the apertureportion in each pixel, which contributes to display, corresponds toregions between the pixel electrode PE and main common electrode CAL andbetween the pixel electrode PE and main common electrode CAR, theseregions being included in the region between the black matrixes BM orthe region between the source line S1 and source line S2.

In the present embodiment, the first horizontal inter-electrode distanceHD between the pixel electrode PE and the common electrode CE is greaterthan the vertical inter-electrode distance VD between the pixelelectrode PE and the common electrode CE. Thus, a high transmittance canbe obtained at the aperture portion. This will be described below moreconcretely.

FIG. 5 is a schematic cross-sectional view of the liquid crystal displaypanel LPN, for explaining alignment states of liquid crystal moleculesLM included in the liquid crystal layer LQ in the embodiment. FIG. 5corresponds to a cross section of the liquid crystal display panel LPNalong the first direction X, and shows only the structure that isnecessary for the description. The example illustrated corresponds tothe case in which the first horizontal inter-electrode distance HDbetween the main pixel electrode PA and the main common electrode CA inthe first direction X is greater than the vertical inter-electrodedistance VD between the main pixel electrode PA and the main commonelectrode CA in the third direction Z.

At the ON time, an electric field is produced between the main pixelelectrode PA and the main common electrode CA. In the region between themain pixel electrode PA and the main common electrode CA, the alignmentof the liquid crystal molecules LM is controlled by this electric field.At this time, the liquid crystal molecules LM maintain an alignmentstate which is relatively parallel to the X-Y plane. The liquid crystallayer LQ including the liquid crystal molecules LM in this alignmentstate has a retardation Δn·d which is necessary for modulating passinglight (Δn is refractive index anisotropy, and d is the thickness ofliquid crystal layer LQ). Specifically, linearly polarized light, whichhas passed through the first optical element OD1, is modulated into sucha polarization state as to be able to pass through the second opticalelement OD2, while the linearly polarized light is passing through theliquid crystal layer LQ. Thus, the light, which has passed through theliquid crystal layer LQ between the main pixel electrode PA and maincommon electrode CA, passes through the second optical element OD2 andcontributes to display. Thereby, a desired transmittance can beobtained.

FIG. 6 is a schematic cross-sectional view of a liquid crystal displaypanel LPN according to a comparative example, for explaining alignmentstates of liquid crystal molecules LM included in a liquid crystal layerLQ. The example illustrated corresponds to the case in which thevertical inter-electrode distance VD between the main pixel electrode PAand the main common electrode CA in the third direction Z is greaterthan the first horizontal inter-electrode distance HD between the mainpixel electrode PA and the main common electrode CA in the firstdirection X.

At the ON time, an electric field is produced between the main pixelelectrode PA and the main common electrode CA. The alignment of theliquid crystal molecules LM in the region between these electrodes iscontrolled by the produced electric field. At this time, the liquidcrystal molecules LM transition into such an alignment state that theliquid crystal molecules LM are raised relative to the X-Y plane. Withthe liquid crystal layer LQ including the liquid crystal molecules LM inthis alignment state, it is difficult to obtain a retardation enough tomodulate passing light. Consequently, compared to the example shown inFIG. 5, the ratio of the light, which passes through the second opticalelement OD2, to the light, which has passed through the liquid crystallayer LQ between the main pixel electrode PA and the main commonelectrode CA, decreases, resulting in a decrease in transmittance.

In order to confirm this phenomenon, the inventor prepared a liquidcrystal display device corresponding to the present embodiment shown inFIG. 5 and a liquid crystal display device corresponding to thecomparative example shown in FIG. 6. The transmittance in each devicewas measured in the ON state with the same voltage applied. In theliquid crystal display device corresponding to the present embodiment,the inter-electrode distance between the main pixel electrode PA and themain common electrode CA was set such that the first horizontalinter-electrode distance HD is 10 μm and the vertical inter-electrodedistance VD is 4 μm. In the liquid crystal display device correspondingto the comparative example, the inter-electrode distance between themain pixel electrode PA and the main common electrode CA was set suchthat the first horizontal inter-electrode distance HD is 2.5 μm and thevertical inter-electrode distance VD is 4 μm. The other conditions werethe same. When the transmittance in the liquid crystal display devicecorresponding to the comparative example was set at 1, the transmittanceof 1.54 was obtained in the liquid crystal display device correspondingto the present embodiment.

According to the present embodiment, as regards the inter-electrodedistance between the main pixel electrode PA of the pixel electrode PE,which is provided on the array substrate AR, and the main commonelectrode CA of the common electrode CE which is provided on thecounter-substrate CT, the first horizontal inter-electrode distance HDis greater than the vertical inter-electrode distance VD. Thus, theraising of the liquid crystal molecules LM at the ON time can besuppressed, and the retardation enough to modulate light passing throughthe liquid crystal layer LQ can be obtained. Accordingly, a decrease intransmittance can be suppressed. Thereby, the degradation in displayquality can be suppressed.

In addition, according to the present embodiment, the second horizontalinter-electrode distance YD is greater than the first horizontalinter-electrode distance HD. Thus, the electric field along the firstdirection X between the main pixel electrode PA and main commonelectrode CA mainly acts on the liquid crystal molecules LM, and theelectric field along the second direction Y between the sub-pixelelectrode PB and sub-common electrode CB hardly acts on the liquidcrystal molecules LM. Specifically, in each pixel, an electric fieldalong the first direction X is mainly produced between the pixelelectrode PE and the common electrode CE, and the liquid crystalmolecules LM are switched by the electric field along the firstdirection X. Therefore, disturbance in alignment of liquid crystalmolecules hardly occurs in the pixel, and a desired display quality canbe obtained.

Moreover, according to the present embodiment, a high transmittance canbe obtained in the inter-electrode gap between the pixel electrode PEand the common electrode CE. Thus, a transmittance per pixel cansufficiently be increased by increasing the inter-electrode distancebetween the main pixel electrode and the main common electrode. Asregards product specifications in which the pixel pitch is different,the peak condition of the transmittance distribution, as shown in FIG.4, can be used by varying the inter-electrode distance. Specifically, inthe display mode of the present embodiment, products with various pixelpitches can be provided by setting the inter-electrode distance, withoutnecessarily requiring fine electrode processing, as regards the productspecifications from low-resolution product specifications with arelatively large pixel pitch to high-resolution product specificationswith a relatively small pixel pitch. Therefore, requirements for hightransmittance and high resolution can easily be realized.

According to the present embodiment, as shown in FIG. 4, if attention ispaid to the transmission distribution in the region overlapping theblack matrix BM, the transmittance is sufficiently lowered. The reasonfor this is that the electric field does not leak to the outside of thepixel from the position of the common electrode CE, and an undesiredlateral electric field does not occur between pixels which neighbor eachother with the black matrix BM interposed, and therefore the liquidcrystal molecules in the region overlapping the black matrix BM keep theinitial alignment state, like the case of the OFF time (or black displaytime). Accordingly, even when the colors of the color filters aredifferent between neighboring pixels, the occurrence of color mixturecan be suppressed, and the decrease in color reproducibility or thedecrease in contrast ratio can be suppressed.

When misalignment occurs between the array substrate AR and thecounter-substrate CT, there are cases in which a difference occurs inthe horizontal inter-electrode distance between the pixel electrode PEand the common electrodes CE on both sides of the pixel electrode PE.However, since such misalignment commonly occurs in all pixels PX, theelectric field distribution does not differ between the pixels PX, andthe influence on the display of images is very small. In addition, evenwhen misalignment occurs between the array substrate AR and thecounter-substrate CT, leakage of an undesired electric field to theneighboring pixel can be suppressed. Thus, even when the colors of thecolor filters differ between neighboring pixels, the occurrence of colormixture can be suppressed, and the decrease in color reproducibility orthe decrease in contrast ratio can be suppressed.

According to the present embodiment, the main common electrodes CA areopposed to the source lines S. In particular, when the main commonelectrode CAL and main common electrode CAR are disposed immediatelyabove the source line S1 and source line S2, respectively, the apertureportion AP can be increased and the transmittance of the pixel PX can beimproved, compared to the case in which the main common electrode CALand main common electrode CAR are disposed on the pixel electrode PEside of the source line S1 and source line S2.

Furthermore, by disposing the main common electrode CAL and main commonelectrode CAR immediately above the source line S1 and source line S2,respectively, the inter-electrode distance between the pixel electrodePE, on one hand, and the main common electrode CAL and main commonelectrode CAR, on the other hand, can be increased, and a lateralelectric field, which is closer to a horizontal lateral electric field,can be produced. Therefore, a wide viewing angle, which is the advantageof an IPS mode, etc. in the conventional structure, can be maintained.

According to the present embodiment, a plurality of domains can beformed in one pixel. Thus, the viewing angle can optically becompensated in plural directions, and a wide viewing angle can berealized.

The above-described example is directed to the case where the initialalignment direction of liquid crystal molecules LM is parallel to thesecond direction Y. However, the initial alignment direction of liquidcrystal molecules LM may be an oblique direction D which obliquelycrosses the second direction Y, as shown in FIG. 2. An angle θ1 formedbetween the second direction Y and the initial alignment direction D is0° or more and 45° or less. From the standpoint of alignment control ofliquid crystal molecules LM, it is desirable that the initial alignmentdirection of liquid crystal molecules LM be a direction in a range of 0°or more and 20° or less, relative to the second direction Y.

The above-described example relates to the case in which the liquidcrystal layer LQ is composed of a liquid crystal material having apositive (positive-type) dielectric constant anisotropy. Alternatively,the liquid crystal layer LQ may be composed of a liquid crystal materialhaving a negative (negative-type) dielectric constant anisotropy.Although a detailed description is omitted, in the case of thenegative-type liquid crystal material, since the positive/negative stateof dielectric constant anisotropy is revered, it is desirable that theabove-described formed angle θ1 be within the range of 45° or more and90° or less, preferably the range of 70° or more and 90° or less.

Since a lateral electric field is hardly produced over the pixelelectrode PE or common electrode CE even at the ON time (or an electricfield enough to drive liquid crystal molecules LM is not produced), theliquid crystal molecules scarcely move from the initial alignmentdirection, like the case of the OFF time. Thus, even if the pixelelectrode PE and common electrode CE are formed of a light-transmissive,electrically conductive material such as ITO, little backlight passesthrough these regions, and these regions hardly contribute to display atthe ON time. Thus, the pixel electrode PE and common electrode CE do notnecessarily need to be formed of a transparent material, and may beformed of an opaque wiring material such as aluminum, silver or copper.

In the above-described example, the structure, in which the storagecapacitance line is disposed immediately below the sub-pixel electrodePB, has been described. However, the gate line may be disposedimmediately below the sub-pixel electrode PB.

In the present embodiment, the structure of the pixel PX is not limitedto the example shown in FIG. 2.

FIG. 7 is a plan view which schematically shows another structureexample at a time when the array substrate AR is viewed from thecounter-substrate side.

This structure example differs from the structure example shown in FIG.2 in that the array substrate AR includes a first shield electrode SE1and a second shield electrode SE2.

The first shield electrode SE1 is electrically connected to the commonelectrode CE and is set at the same potential as the common electrodeCE. The first shield electrode SE1 extends in the first direction X, andis opposed to each of the gate lines G. In the example illustrated, twofirst shield electrodes SE1 are arranged in parallel with a distance inthe second direction Y.

The second shield electrode SE2 is continuous with the first shieldelectrode SE1, and is set at the same potential as the common electrodeCE. In addition, the second shield electrode SE2 extends in the seconddirection Y, and is opposed to each of the source lines S. In theexample illustrated, two second shield electrodes SE2 are arranged inparallel with a distance in the first direction X.

The first shield electrodes SE1 and second shield electrodes SE2 areformed in the same layer as the pixel electrode PE, and can be formed ofthe same material as the pixel electrode PE. Specifically, when thepixel electrode PE is formed on the second interlayer insulation film 12in the example shown in FIG. 3, the first shield electrodes SE1 andsecond shield electrodes SE2 are formed on the second interlayerinsulation film 12 and are covered with the first alignment film AL1.The first shield electrodes SE1 and second shield electrodes SE2 arespaced apart from the pixel electrode PE. The array substrate AR of thisstructure example is combined with the counter-substrate CT includingthe common electrode CE shown in FIG. 2.

FIG. 8 is a schematic cross-sectional view, taken along line B-B in FIG.7, showing a cross-sectional structure of a liquid crystal display panelwhich is combined with the array substrate AR shown in FIG. 7. FIG. 8shows only parts which are necessary for the description.

The gate line G is located under the first shield electrode SE1 or underthe sub-common electrode CB. The sub-common electrode PB is opposed tothe first shield electrode SE1. The horizontal inter-electrode distancein the second direction Y between the sub-pixel electrode PB and thesub-common electrode CB is equal to the horizontal inter-electrodedistance in the second direction Y between the first shield electrodeSE1 and the sub-common electrode CB. Specifically, in the structureexample illustrated, the second horizontal inter-electrode distance YDcorresponds to the inter-electrode distance in the second direction Ybetween the sub-pixel electrode PB and each of the sub-common electrodeCB and the first shield electrode SE1. In this structure example, too,the first horizontal inter-electrode distance HD is less than the secondhorizontal inter-electrode distance YD, and is greater than the verticalinter-electrode distance VD.

According to the structure example shown in FIG. 7 and FIG. 8, the sameadvantageous effects as with the structure example shown in FIG. 2, etc.can be obtained. In addition, with the provision of the first shieldelectrodes SE1, an undesired electric field from the gate lines G can beshielded. Therefore, the degradation in display quality can be furthersuppressed. Moreover, with the provision of the second shield electrodesSE2, an undesired electric field from the source lines S can beshielded. Therefore, the degradation in display quality can be furthersuppressed.

FIG. 9 is a plan view which schematically shows another structureexample of the pixel PX at a time when the liquid crystal display panelLPN shown in FIG. 1 is viewed from the counter-substrate side.

This structure example differs from the structure example shown in FIG.7 in that the pixel electrode PE includes a plurality of main pixelelectrodes PA which are arranged substantially in parallel with aninterval in the first direction X, and that the common electrode CEincludes a main common electrode CA between the neighboring main pixelelectrodes PA, in addition to the main common electrode CE being formedin a grid shape in a manner to surround the pixel PX.

Specifically, the pixel electrode PE includes a main pixel electrodePA1, a main pixel electrode PA2 and a sub-pixel electrode PB. The mainpixel electrode PA1, main pixel electrode PA2 and sub-pixel electrode PBare mutually electrically connected. The main pixel electrode PA1 andmain pixel electrode PA2 are arranged substantially in parallel with aninterval in the first direction X. The main pixel electrode PA1 and mainpixel electrode PA2 linearly extend in the second direction Y from thesub-pixel electrode PB to the vicinity of the upper side end portion ofthe pixel PX and to the vicinity of the lower side end portion of thepixel PX. The sub-pixel electrode PB extends along the first directionX. The sub-pixel electrode PB is located in an area overlapping thestorage capacitance line C1, and is electrically connected to theswitching element SW via the contact hole CH.

The common electrode CE includes a main common electrode CAL, a maincommon electrode CAR, a main common electrode CAC, a sub-commonelectrode CBB and a sub-common electrode CBU. The main common electrodeCAL, main common electrode CAR, main common electrode CAC, sub-commonelectrode CBB and sub-common electrode CBU are mutually electricallyconnected.

The main common electrode CAL, main common electrode CAR and main commonelectrode CAC are arranged substantially in parallel with intervals inthe first direction X, and extend in the second direction Y. In thepixel PX, the main common electrode CAL is located on the left side endportion, the main common electrode CAR is located on the right side endportion, and the main common electrode CAC is located between the mainpixel electrode PA1 and main pixel electrode PA2.

The sub-common electrode CBB and sub-common electrode CBU are arrangedsubstantially in parallel with an interval in the second direction Y,and extend in the first direction X. In the pixel PX, the sub-commonelectrode CBB is disposed at the lower side end portion, and thesub-common electrode CBU disposed at the upper side end portion. Thesub-pixel electrode PB is disposed between the sub-common electrode CBBand the sub-common electrode CBU.

Paying attention to the positional relationship between the pixelelectrode PE and the common electrode CE, the main pixel electrodes PAand the main common electrodes CA are alternately arranged along thefirst direction X, and the sub-pixel electrode PB and the sub-commonelectrodes CB are alternately arranged along the second direction Y.Specifically, one main pixel electrode PA1 is located between the maincommon electrode CAL and main common electrode CAC which neighbor eachother, and one main pixel electrode PA2 is located between the maincommon electrode CAC and main common electrode CAR which neighbor eachother. The main common electrode CAL, main pixel electrode PA1, maincommon electrode CAC, main pixel electrode PA2 and main common electrodeCAR are arranged in the named order along the first direction X. Inaddition, one sub-pixel electrode PB is located between the sub-commonelectrode CBB and sub-common electrode CBU which neighbor each other,and the sub-common electrode CBB, sub-pixel electrode PB and sub-commonelectrode CBU are arranged in the named order along the second directionY.

The first horizontal inter-electrode distance between the main commonelectrode CAL and main pixel electrode PA1, the first horizontalinter-electrode distance between the main common electrode CAC and mainpixel electrode PA1, the first horizontal inter-electrode distancebetween the main common electrode CAC and main pixel electrode PA2, andthe first horizontal inter-electrode distance between the main commonelectrode CAR and main pixel electrode PA2 are substantially equal (HD).

In this structure example, too, the liquid crystal molecules LM, whichare initially aligned in the second direction Y at the OFF time, canform many domains in each pixel PX in the state in which an electricfield is produced between the pixel electrode PE and common electrode CEat the ON time, and the viewing angel can be increased.

As has been described above, according to the present embodiments, aliquid crystal display device which has a good display quality can beprovided.

While certain embodiments have been described, these embodiments havebeen presented by way of example only, and are not intended to limit thescope of the inventions. Indeed, the novel embodiments described hereinmay be embodied in a variety of other forms; furthermore, variousomissions, substitutions and changes in the form of the embodimentsdescribed herein may be made without departing from the spirit of theinventions. The accompanying claims and their equivalents are intendedto cover such forms or modifications as would fall within the scope andspirit of the inventions.

What is claimed is:
 1. A liquid crystal display device comprising: afirst substrate including a cross-shaped pixel electrode which isdisposed in a pixel having a less length in a first direction than in asecond direction crossing the first direction and includes a main pixelelectrode extending in the second direction and a sub-pixel electrodeextending in the first direction, the first substrate further includinga first alignment film which covers the pixel electrode and is subjectedto alignment treatment in a first alignment treatment direction; asecond substrate including a common electrode which includes main commonelectrodes extending in the second direction on both sides of the mainpixel electrode and sub-common electrodes extending in the firstdirection on both sides of the sub-pixel electrode, the second substratefurther including a second alignment film which covers the commonelectrode and is subjected to alignment treatment in a second alignmenttreatment direction which is parallel to the first alignment treatmentdirection; and a liquid crystal layer including liquid crystal moleculesheld between the first substrate and the second substrate, wherein afirst horizontal inter-electrode distance in the first direction betweenthe main pixel electrode and the main common electrode is less than asecond horizontal inter-electrode distance in the second directionbetween the sub-pixel electrode and the sub-common electrode and isgreater than a vertical inter-electrode distance between the main pixelelectrode and the main common electrode in a third direction which isperpendicular to the first direction and the second direction.
 2. Theliquid crystal display device of claim 1, wherein the second horizontalinter-electrode distance is double or more greater than the firsthorizontal inter-electrode distance.
 3. The liquid crystal displaydevice of claim 2, wherein the second horizontal inter-electrodedistance is about three times the first horizontal inter-electrodedistance.
 4. The liquid crystal display device of claim 3, wherein alength of the main pixel electrode in the second direction is greaterthan a length of the sub-pixel electrode in the first direction.
 5. Theliquid crystal display device of claim 4, wherein an initial alignmentdirection of the liquid crystal molecules in a state, in which anelectric field is not produced between the pixel electrode and thecommon electrode, is substantially parallel to a direction of extensionof the main pixel electrode.
 6. The liquid crystal display device ofclaim 5, wherein the first alignment treatment direction is identical tothe second alignment treatment direction, and the liquid crystalmolecules are splay-aligned between the first substrate and the secondsubstrate.
 7. The liquid crystal display device of claim 6, furthercomprising a first polarizer which is disposed on an outer surface ofthe first substrate and includes a first polarization axis, and a secondpolarizer which is disposed on an outer surface of the second substrateand includes a second polarization axis having a positional relationshipof crossed Nicols with the first polarization axis, the firstpolarization axis being perpendicular or parallel to the initialalignment direction.
 8. The liquid crystal display device of claim 4,wherein the first substrate further includes gate lines extending in thefirst direction and located under the sub-common electrodes, a storagecapacitance line extending in the first direction and located under thesub-pixel electrode, source lines extending in the second direction andlocated under the main common electrodes, and first shield electrodeshaving the same potential as the common electrode, extending in thefirst direction, opposed to the gate lines, and covered with the firstalignment film, and an inter-electrode distance in the second directionbetween the sub-pixel electrode and the first shield electrode is equalto the second horizontal inter-electrode distance.
 9. The liquid crystaldisplay device of claim 6, wherein the first substrate further includessecond shield electrodes having the same potential as the commonelectrode, extending in the second direction, opposed to the sourcelines, and covered with the first alignment film.
 10. A liquid crystaldisplay device comprising: a first substrate including a cross-shapedpixel electrode which includes a sub-pixel electrode extending a firstdirection and a main pixel electrode extending in a second directioncrossing the first direction, the main pixel electrode having a greaterlength than the sub-pixel electrode, the first substrate furtherincluding a first alignment film which covers the pixel electrode and issubjected to alignment treatment in a first alignment treatmentdirection; a second substrate including a common electrode whichincludes main common electrodes extending in the second direction onboth sides of the main pixel electrode and sub-common electrodesextending in the first direction on both sides of the sub-pixelelectrode, the second substrate further including a second alignmentfilm which covers the common electrode and is subjected to alignmenttreatment in a second alignment treatment direction which is paralleland identical to the first alignment treatment direction; and a liquidcrystal layer including liquid crystal molecules held between the firstsubstrate and the second substrate, wherein an initial alignmentdirection of the liquid crystal molecules in a state, in which anelectric field is not produced between the pixel electrode and thecommon electrode, is substantially parallel to a direction of extensionof the main pixel electrode, and a first horizontal inter-electrodedistance in the first direction between the main pixel electrode and themain common electrode is less than a second horizontal inter-electrodedistance in the second direction between the sub-pixel electrode and thesub-common electrode and is greater than a vertical inter-electrodedistance between the main pixel electrode and the main common electrodein a third direction which is perpendicular to the first direction andthe second direction.
 11. The liquid crystal display device of claim 10,wherein the second horizontal inter-electrode distance is double or moregreater than the first horizontal inter-electrode distance.
 12. Theliquid crystal display device of claim 11, wherein the second horizontalinter-electrode distance is about three times the first horizontalinter-electrode distance.
 13. The liquid crystal display device of claim12, further comprising a first polarizer which is disposed on an outersurface of the first substrate and includes a first polarization axis,and a second polarizer which is disposed on an outer surface of thesecond substrate and includes a second polarization axis having apositional relationship of crossed Nicols with the first polarizationaxis, the first polarization axis being perpendicular or parallel to theinitial alignment direction.